Mobile communications systems, such as cellular or personal communications services (PCS) systems, are made up of a plurality of cells. Each cell provides a radio communications center in which a mobile station establishes a call with another mobile station or wireline unit connected to a public switched telephone network (PSTN). Each cell includes a radio base station, with each base station connected to a base station controller or mobile switching center that controls processing of calls between or among mobile stations or mobile stations and PSTN units.
Various wireless protocols exist for defining communications in a mobile network. One such protocol is a time-division multiple access (TDMA) protocol, such as the TIA/EIA-136 standard provided by the Telecommunications Industry Association (TIA). With TIA/EIA-136 TDMA, each channel carries a frame that is divided into six time slots to support multiple (3 or 6) mobile stations per channel. Other TDMA-based systems include Global System for Mobile (GSM) communications systems, which use a TDMA frame divided into eight time slots (or burst periods).
Traditional speech-oriented wireless systems, such as the TIA/EIA-136 and GSM TDMA systems, utilize circuit-switched connection paths in which a line is occupied for the duration of the connection between a mobile station and the mobile switching center. Such a connection is optimum for communications that are relatively continuous, such as speech. However, data networks such as local area networks (LANs), wide area networks (WANs), and the Internet use packet-switched connections, in which communication between nodes on a communications link is by data packets. Each node occupies the communications link only for as long as the node needs to send or receive data packets. Popular forms of communications over packet-switched networks include electronic mail, web browsing, text chat sessions, file downloads, and other types of data transfers.
Several packet-switched wireless connection protocols have been proposed to provide more efficient connections between a mobile station and a data network. One such protocol is the General Packet Radio Service (GPRS) protocol, which complements existing GSM systems. Another technology that builds upon GPRS is the Enhanced Data Rate for Global Evolution (EDGE) technology, which offers even higher data rates. The enhancement of GPRS by EDGE is referred to as Enhanced GPRS (EGPRS). Another variation of EGPRS is the COMPACT technology. GPRS, EGPRS, and COMPACT are established by the European Telecommunications Standards Institute (ETSI).
The packet-switched wireless connection protocols provide efficient access to data networks, such as the Internet, LANs, WANs, and the like. A growing use of such data networks is for voice and other forms of real-time or streaming communications (such as video, audio and video, multimedia, and so forth). Various protocols have been defined to enable such real-time or streaming communications over the data networks, with one popular type of packet-switched network being the Internet Protocol (IP) network.
In some wireless communication systems, mobile stations are able to enter into a discontinuous transmission (DTX) mode. When a mobile station is not transmitting, such as when a user is not talking, and there is no other traffic to communicate, the mobile station can enter into DTX mode to save power and also to reduce interference with other mobile stations. During DTX, a channel between the mobile station and the base station is idle (that is, no traffic is being communicated). However, other mobile stations do not have access to the idle channel, since the channel is dedicated to the voice user. This is to ensure that the voice user can quickly start communicating over the channel once the user resumes talking. As a result, available bandwidth is wasted in some mobile communications systems.